01 - Preheat the oven to 320°F. Grease and line an 8-inch square cake pan with parchment paper.
02 - Sift together flour, ground ginger, cinnamon, nutmeg, baking powder, and salt in a large bowl; set aside.
03 - Gently melt butter, brown sugar, golden syrup, and black treacle in a saucepan over low heat, stirring until smooth. Remove from heat and allow to cool slightly.
04 - In a separate bowl, whisk together eggs and milk until combined.
05 - Pour the syrup mixture into the dry ingredients and stir to combine. Add the egg and milk mixture and mix until smooth and free of lumps.
06 - Fold in the finely chopped stem ginger and 2 tablespoons of ginger syrup.
07 - Pour the batter into the prepared pan and smooth the surface.
08 - Bake for 45 to 50 minutes or until a skewer inserted in the center comes out clean.
09 - Allow to cool in the pan for 10 minutes before transferring to a wire rack. Serve warm or at room temperature.